In papermaking, the question of how to increase the dewatering amount from the wet paper web in the press part in order to improve productivity is an important issue. The means adopted for increasing the dewatering amount of the press part include: raising the pressure applied by the press roll, increasing the hardness of the press roll, and other methods; among these, the method of improving the dewatering effect by interposing a shoe press belt to extend the time during which pressure is applied between the roll and the felt during pressing has become widespread in recent years.
Recently, the number of shoe press belts has also increased, in which a plurality of grooves is provided in the felt-side surface for efficiently draining the squeezed water. For example, the press belt in FIG. 1 (according to Patent document 1) is a shoe press belt in which the water draining effect has been boosted by providing a plurality of grooves in the felt surface. The groove configuration of this shoe press belt is made to prevent the occurrence of cracks in the bottom corner parts of the groove by providing a smooth transition rotundity between the two sidewalls, diverging upward towards the opening region, and the groove bottom part.
Regarding the press jacket in FIG. 2 (Patent document 2), the press jacket is provided with a plurality of grooves and/or blind holes wherein the sidewalls are provided, in the opening region, with an inclined surface and/or a spherical section extending along a prescribed curve in order to prevent a reduction of the volume when a compression load is applied.
The shoe press belt of FIG. 3 (Patent document 3) is characterized in that, in a belt for carrying a felt for squeezing water from a wet paper web between a press roll and a shoe, water drain grooves are provided in the felt-side surface of the shoe press belt which is pressed under high pressure when it approaches the press roll; wherein the groove configuration has outwardly curved sidewalls.
The shoe press belt in FIG. 4 (Patent document 4) is characterized in that, for preventing the occurrence and development of cracks, the bottom of the water drain grooves 9a in the end part-adjoining region S3 in the axis direction, which comprises either one of the end part-adjoining region S2 in the axis direction of the press shoe 10 or the end part-adjoining region S1 in the axis direction of the press roll 11, penetrates further to the reinforcing layer 12 than the bottom of water drain grooves 9b in regions other than the end part-adjoining region S3.